Centrifuge



Dec. 9, 1958 G. LINKE ET AL CENTRIFUGE Filed May 23, 1955 INVENTORS GEHHARD L/NKE HANS-HEINRICH HULSEN ATTORNEYS United States PatentO CENTRIFUGE Gerhard Linke, Mulheim (Ruhr), and Hans-Heinrich Hillsen, ]Duisburg, Germany, assignors to Siebtechnik G. m. b. ll-L, Mulheirn (Ruhr), Germany Application May 23, 1955, Serial No. 510,406 in Germany September 16, 1949 Public Law 619, August 23, 1954 Patent expires September 16, 1969 12 Claims. (11. 210-147 This invention relates to improvements in centrifuges.

It refers in particular to centrifuges of the kind having a screening drum, a discharge worm, or the like, and a transmission drive connecting the aforesaid two members.

It is known in the art to provide centrifuges for continuous operation with a screening drum and a conical or cylindrical discharge member having spiral-shaped conveying and/or scraping means on its outer surface. Both members are usually mounted on horizontal or vertical shafts and rotate at diflferent speeds.

This centrifuge is driven from a transmission drive which provides for the difference in speed of the two centrifuge members.

This drive may consist of a spur gear drive, an epicyclic drive, an internal gear drive, or a cycloidal gear drive as it is described in a pamphlet on Motor Gears by Cyclo G. m. b. H., Munich, Germany.

These transmission drives, especially the cycloidal gear drives have the advantage ofpermitting an arrangement of transmission wherein one shaft remains stationary while the gear casing and another member rotate. Thereby a differential movement is brought about between the gear casing and the other rotating member of the drive which are connected respectively with the screening drum and the scraper-bearing or worm drum of the centrifuge, in the case of a cycloidal gear drive the other rotating member being an eccentric disk of the drive.

However, these drives, especially the cycloidal drives are often liable to be damaged by an overload or an obstruction interfering'with the differential movement of the screening drum relative to the discharge drum, which disturbances may be caused by foreign matter entering the inter-space between both drums, and may provoke the occurrence of sudden overloads in the drive.

It is an object of the invention to provide an improved drive for centrifuges wherein damage to the drive due to the occurrence of sudden overloads in operation is avoided.

The invention attains this object by providing a centrifuge having a transmission drive of the above mentioned type with an overload coupling between the shaft of the drive which remains stationary during normal operations, and the framework of the centrifuge.

In a preferable embodiment of the invention the maximal torque of this overload coupling is adjustable.

The coupling may consist of a multiple disk clutch, a hydraulic clutch, or a cone clutch.

In normal operation the coupling which is attached to the centrifuge frame engages the central shaft of the transmission drive and prevents rotation of the shaft. But, as soon as the differential movement of the centri fuge members is blocked, and the torque thereby exercised on the stationary shaft, exceeds the maximal torque to which the overload coupling has been designed or adjusted by adjusting means such as turnbuckles, screws, and the like, the clutch slips and the stationary shaft of the drive begins to rotate. The heat originated ice by the slipping of the clutch may be eliminated for instance by way of a system of lubrication by oil circulation until the centrifuge stops.

Another object of the invention is to avoid an unduly prolonged slipping of the clutch by providing switch means connected with the normally stationary shaft of the drive, which switch means interrupt the operation of the motor driving the centrifuge in case of disturbances.

Operation of the motor may be interrupted directly by means of a switch mounted on to the stationary shaft and operating, for instance, as a centrifugal switch when the shaft rotates.

The switch means may also be actuated by a protrusion such as a pin fastened to the stationary shaft.

According to another feature of the invention the stationary shaft is connected with a small gear-pump.

When the shaft begins to rotate, oil pressure is created in a conduit leading to the switch means for interrupting the movement of the motor, which pressure actuates the switch.

The several objects and advantages referred to above will become more apparent upon reference to the accompanying drawings, wherein:

Figure 1 is a cross sectionalview of the centrifuge according to this invention.

Figure 2 is a sectional view of the overload clutch shown in Figure 1 including means for adjusting the maximal torque of the clutch.

Figure 3 shows an embodiment of the switch means according to the invention as a centrifugal switch; and

Figure 4 shows another embodiment of the overload coupling as a hydraulic coupling.

Referring now to the drawings in detail, and more particularly to Figure 1, reference numeral indicates the centrifuge housing which comprises an internal frame 11. A screening drum 12 is mounted in the housing for rotation on a shaft 13.

A scraper bearing discharge drum 14 is mounted for rotation on a hollow shaft 15 which co-centrically surrounds shaft 13.

Shaft 15 is rigidly connected with the cylindrical gear casing 16 of a cycloidal drive comprising eccentric disk portions 17. These portions engage rollers 18 mounted on a disk 19 flangedly connected to the lower end of shaft 13.

The cycloidal drive casing 16 is rigidly connected by means of a hollow shaft 20 to a first bevel gear 21 which engages a second bevel gear 22 mounted on a driving shaft 23 arranged at a right angle to the hollow shaft 20.

Shaft 23 is rotated by means of a motor (not shown).

The eccentric disk portions 17 of the cycloidal drive rotate around a central disk 24 flangedly connected to the shaft 25 which is mounted co-axially in the hollow shaft 20, and is held stationary under normal operation by means of a multiple disk clutch 26, the inner disks 27 of which are mounted at the lower end on the shaft 25, while the outer disks 28 are displaceably mounted in the clutch housing 29 which is rigidly attached to the inner frame 11 of the centrifuge.

Friction between the disks 27 and 28 is created, for instance, by springs 30 and 31; the pressure of these springs on the disk assembly and together therewith the maximal torque of the clutch are adjusted by suitable means such as adjusting screws 32 for altering the tension of the springs.

A small gear pump 33 is mounted in the lower part of the clutch housing 29. Gear 34 of the gear pump 33 is mounted on the lower end of shaft 25, while an oil conduit 35 connects the gear pump 33 with a switch 36 which is in turn connected to the motor (not shown), by connecting means 37.

Referring now more particularly to the embodiment of the switch means shown in Figure 3, these means represent a centrifugal switch 38 which is mounted at the lower end of shaft in replacement of the .gear pump 33.

In its circumference the centrifugal switch 38 possesses a recess 39 wherein there is located a lever 40 pivotally mounted on disk 38 at 41.

A restoring spring 42 is provided to retain lever 40 in its initial position in the housing by acting against the. centrifugal forces which try to move the lever into the position indicated by dash-and-dotted lines at 40.

At its shorter end the lever 40 is provided with a contact plate 43 which contacts the terminal 44 of an electric circuit 45 actuated when lever 40 adopts the position at 40' whereby the circuit 45 is closed.

The embodiment of the overload coupling shown in Figure 4 represents a hydraulic coupling which replaces the multiple disk clutch 29.

This multiple disk coupling comprises a housing 46 rigidly attached to the inner frame 11 of the centrifuge, which housing is filled with fluid and provided with a fluid discharge outlet 47 at its bottom.

A disk 48 is mounted on the lower end of shaft 25 and provided with blades 49, thereby acting as an impeller for the hydraulic clutch when shaft 25 rotates.

In a central recess 50 in the lower end of shaft 25 is supported co-axially the downwardly extending shaft 51 bearing the gear 34 of gear pump 33 which pump is mounted on the housing 46 of the hydraulic clutch in the same way as on the housing 29 of the multiple disk clutch as shown in Figure 1.

Under normal operation the motor (not shown) drives shaft 23 and bevel gears 22 and 21. From the latter gear power is transmitted to the cycloidal gear casing 16 and from there at the same rate of speed through shaft 15 to the discharge drum 14. Concurrently power is transmitted from the gear casing 16 by way of parts 17, 18 and 19 of the cycloidal gear drive at a different rate of speed to the shaft 13 and the screening drum 12. During this normal operation shaft 25 and disk 24 remain stationary, shaft 25 being held against rotation by means of the overload clutch. If, however, an obstruction occurs in the space 52 between drums Hand 14, these drums will be forced to rotate at even speed, there by forcing a rotation of disk 24 and together therewith of shaft 25 as soon as the torque created by the rotation at equal speed of both drums exceeds the maximal torque to which the overload clutch has been adjusted, for instance by adjusting means 32.

In the hydraulic clutch (Figure 4, an adjustment of the maximal torque can be made for instance, by exchanging the fluid for one of a different viscosity).

As soon as shaft 25 begins to rotate, it causes also a corresponding rotation of gear 34 in gear pump 33, whereby oil pressure is created in conduit 35. This pressure actuates the switch 36 and causes the same to interrupt, by way of connections 37, the operation of the motor-driven shaft 23. Thereby any overheating of the clutch and damage to the cycloidal gear drive are successfully prevented.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions, and, accordingly, it is desired to comprehend such modification within this invention as may fall within the scope of the appended claims. This applying especially to the cycloidal drive which may as well be replaced by a transmission drive of a different type permitting two members to rotate at different speeds if a third member remains stationary.

What we claim is:

l. A centrifuge comprising a screening drum, a discharge member cooperating with said screening drum, and a transmission drive comprising a first and a second shaft connected with said screening 'drum and said discharge member respectively, said transmission drive including an input shaft adapted for being driven to impart rotation at different speeds to said screening drum and said discharge member; a third shaft operatively interconnected with said screening drum and said discharge member and forming a reaction member which remains stationary during rotation of said screening drum and said discharge member at different speeds and rotates if said screening drum and said discharge member rotate at equal speeds; a centrifuge frame; and a brake having a first and a second member normally stationary relative to each other but being relatively movable upon development of a predetermined torque therebetween, said first member being rigidly mounted in said frame, said second member being attached to the free end of said third shaft, and means operable in response to relative movement between said first and second members for interrupting the supply of power to said input shaft.

2. In a centrifuge having a screening drum, a discharge member cooperating with said screening drum, and a centrifuge frame; the combination of a transmission gear drive comprising a first and second shaft connected with said screening drum and said discharge member respectively, said drive including an input shaft adapted for being driven for imparting rotation at different speeds to said first and second shafts, said transmission drive further comprising a third shaft forming a reaction member for the transmission drive and remaining stationary during rotation of said first and second shafts at different speeds, and adapted to rotate if said first and second shafts rotate at equal speeds; a brake comprising a first and a second member releasably fixed relatively, said first member being attached rigidly to said frame, said second member being drivingly connected with said third shaft, said brake being operable normally to hold said third shaft stationary when said first and second shafts rotate at said different speeds and the said first and second members thereof being relatively movable to permit rotation of said third shaft when said first and second shafts rotate at even speed thereby imparting to said third shaft a torque greater than the minimum required to cause relative movement between the members of said brake; and switch means adapted for being actuated by said third shaft when the latter rotates, said switch means being operable to interrupt the supply of power to said input shaft, and thus to stop said screening drum and discharge member.

3. A centrifuge comprising, in combination, a pair of cooperating centrifuging members, a transmission gear drive having an input shaft and comprising first, second, and third shaft means, said first and second shaft means being connected with and imparting different speeds to each member of said pair of cooperating centrifuging members, said third shaft means forming a reaction member and being stationary during rotation of said pair of centrifuging members at predetermined different speeds, said third shaft means being adapted to rotate if said pair of centrifuging members rotate at equal speeds; a brake connected between said third shaft means and a stationary point operable for holding said third shaft means stationary while said pair of centrifuging members rotates at said different speeds, and also operable for permitting rotation of said third shaft means when said pair of centrifuging members rotate at equal speeds, and means operable in response to rotation of said third shaft means adapted for interrupting the driving of said input shaft thereby to halt the centrifuge.

4. A centrifuge-comprising, in combination, a pair of cooperating centrifuging members, a transmission gear drive having an input shaft and comprising first, second, andthird shaftmeans, said first and second shaft means being connected with and imparting different speeds to each member of said pair of cooperating centrifuging members, said third shaft means forming a reaction member and being stationary during rotation of said pair of centrifuging members at said different speeds, and being adapted to rotate if said pair of centrifuging members rotates at equal speeds; a brake releasably holding said third shaft mean's stationary while said pair of centrifuging members rotates at different speeds, and operable for permitting said third shaft means to rotate when said pair of centrifuging members rotate at equal speeds, and switch means adapted to be actuated by said third shaft when rotating adapted for interrupting the supply of power to said input shaft so as to interrupt operation of said transmission gear drive, and thus to stop said pair of centrifuging members.

5. A centrifuge as described in claim 4, wherein said brake is a multiple disk brake, having some disks stationarily supported and other disks connected with said third shaft means.

6. A centrifuge as described in claim 4, wherein said brake is a hydraulic brake.

7. A centrifuge as described in claim 4, wherein adjusting means are provided for adjusting the minimum torque of said brake, at which said brake releases said third shaft means for rotation.

8. A centrifuge as described in claim 4, wherein said switch means consist of a centrifugal switch adapted for interrupting the operation of said drive and stopping said pair of centrifuging members upon rotation of said third shaft.

9. A centrifuge as described in claim 4, wherein said switch means comprise a gear pump, a gear in said gear pump being connected to the free end of said third shaft, a switch for controlling an electric current, conduit means between said gear pump and said switch for imparting pressure to said switch upon rotation of said third shaft and said gear in said gear pump connected therewith, said switch causing said electric current to interrupt the operation of said transmission gear drive and stop said pair of centrifuging members upon receiving pressure from said gear pump.

10. A centrifuge as described in claim 4, wherein said transmission. gear drive is a cycloidal gear drive.

11. A centrifuge as described in claim 5, wherein said multiple disk brake comprises resilient means for urging the disks thereof into friction engagement, and adjusting means for adjusting the force of said resilient means and together therewith the minimum torque at which said brake releases said third shaft means for rotation.

12. A centrifuge as described in claim 6, wherein said hydraulic brake comprises a stationary casing being filled with a fluid of determined viscosity, an impeller connected to said third shaft means, a turbine wheel connected to said switch means, and means for exchanging said fluid in said casing for a fluid of a different viscosity, thereby altering the minimum torque of said brake at which the latter releases said third shaft means for rotation.

References Cited in the file of this patent UNITED STATES PATENTS 628,094 Hooper July 4, 1899 1,571,457 Orr Feb. 2, 1926 1,749,368 Behr Mar. 4, 1930 1,921,296 Harkness Aug. 8, 1933 1,926,995 Harkness Sept. 12, 1933 

